Method of constructing furnace parts



y 1965 c. F. WARGA ETAL 3,197,528

METHOD OF CQNSTRUCTING FURNACE PARTS Filed April 11, 1962 Furnace Door Sheii Fill Shell with Plastic Chrome Ore Refractory Containing Sodium Silicate Binder Cover Exposed Refractory Face with Impervious Sheet Pending Hardening Treatment Harden Retractory(after Removing Cover Sheet) Solely by Irrodiating Exposed Face with Infra-Red Source Heated Above tOOOF.

INVENTORS CHARLES F. WARGA RUSSEL A. MiLLER QM; QELKMZM ATTORNEYS United States Patent 3,l7,528 {3F fiflhll TRUiCTlNG FURNACE PARTS Charles F. Warga, Eenliintown, and Russel A. Miller, West Chester, Pa, assignors to Howe Sound (Iompany, New Yorlr, N.Y., a corporation of Delaware Filed Apr. 11, 1962., tier. No. 186,626 7 tillaims. (tCl. 264-450) This invention relates to furnace parts, such as doors for open hearth furnaces, and is directed, more particularly, to a new and improved method of constructing furnace parts.

Because of the very high temperatures maintained in the normal operation of a furnace, such as an open hearth, various parts of the furnace, for instance, its doors are provided with an inner wall of a refractory material. In a conventional method of constructing a door for an open hearth furnace, a door shell is rammed with a plastic material composed of a primary chrome ore mixed with odium silicate and a minor amount of clay or other additive. The plastic material is dried in place, for ex ample, by means of steam pipes on the metal side of the door; this may take from twenty-four to seventy-two hours. In the process, the sodium silicate bonding material sometimes tends to form a slain on the top surface of the refractory material. As a result, drying is inhibited and there is a tendency to produce a laminar structure which decreases service life of the door.

It is an object of the present invention, therefore, to provide a new and improved method of constructing furnace parts whereby longer service life is achieved.

Another object of the present invention is to provide a l cw and improved method of constructing furnace parts, which method requires less time than heretofore needed.

Still another object of the present invention is to provide a new and improved method of constructing furnace parts which include a refractory material wherein the amount of buckling and laminations are significantly reduced as compared with the product of conventional methods of construction.

The method of constructing furnace parts in accord ance with the present invention is adapted to produce parts of the type comprised of a refractory material enclosed by a shell and includes the steps of introducing a plastic, heat-hardenable, refractory material into the shell whereby a surface of the refractory material is exposed and irradiating the exposed surface of the refractory ma terial with radiant energy having a principal component in the infra-red portion of the radiant energy spectrum for a period of time sufiicient to harden the refractory material while minimizing buckling and the formation of laminations therein.

The accompanying flow sheet illustrates the process of the invention as applied to the preparation of a furnace door insulated with a chrome ore refractory.

Following is a detailed description of a presently preferred embodiment of the invention.

In a typical application of the present invention, steel doors for an open hearth furnace are constructed. These doors include a steel shell, for example, of pan-like, rectangular configuration 43 inches wide, 54 inches high, and inches thick.

A mixture is prepared of chrome ore, clay, sodium silicute and water in the following proportions by weight:

Percent Chrome ore 89 Clay 3 Sodium silicate 8 Water, as required for desired plasticity.

3, 1 ,5'213 Patented July 27, 195

It has been found that a suitable mixture can be prepared of the constituents in the following ranges (by weight):

Percent Chrome ore to 92. Clay -c 2 to 4 Sodium silicate 6 to 10 Water, as required for desired plasticity.

The chrome ore referred to is composed primarily of iron chromite and contains miscellaneous impurities. It may be obtained from readily available sources in the Phillipines, Transvaal, Rhodesia, or other locations. The clay referred to above may be any type of plastic clay, such as bentonitc, ball clay, etc.

The resulting mixture is a plastic, heat-'hardenable, refractory material and it is introduced into the door shell in a suflicient quantity to fill the shell. A rammer or tamper is used in a conventional manner to assure a complete filling. Alternatively, the refractory mix may be introduced by gunning, spraying or casting in accordance with known techniques. Since the shell is of panlike configuration, a surface of the refractory material is exposed. This surface may be leveled by means of a scraper used in a conventional way so that the refractory material is leveled to the side of the shell. In certain applications, the exposed surface of the refractory ma terial may be scraped slightly below the sides of the shell. For example, in a door having an internal thickness of five inches, material was scraped off to a distance onequarter inch below the sides of the shell. In the application described herein, the shell reccived fourteen hundred pounds of plastic, heat-hardenable refractory material.

The door shell with the plastic material is then placed under a source of infra-red radiation with the exposed surface of the refractory material facing upward in close proximity to the source; a spacing of on the order of six inches has been found suitable. For example, gas-fired infra-red generators may be utilized. Such a source provides a principal component at a wave length of approximately three microns. A suflicient number of units are grouped to provide a distributed source of infra-red energy essentially entirely coextensive with the exposed surface of the refractory material. The source is energized so that its surface temperature is within a range providing greatest efiicicncy. For a typical gas-fired unit, the temperature is preferably in a range from 1,600 degrees to 1,650 degrees F.

Alternatively, electrically energized bulb type units may be employed having a principal output component at a wave length of one micron and an operating temperature at approximately 4,500 degrees F. Still another appropriate source is comprised of a Nichrome wire electrically energized to provide a principal output component at a wave length of four microns and an operating temperature of approximately 1,200 degrees F. Preferably, the source should emit infra-red radiation having a principal component in a range of wave lengths in the radiant energy spectrum between 0.5 and 6 microns and have an operating temperature greater than 1,000 degrees F.

Irradiation is continued for a period of time sufiicient to harden the refractory material while minimizing buckling and the formation of laminations therein.

In a typical application, thermo-couples of conventional construction were used to measure the temperature within one quarter inch of the exposed surface of the refractory material and on the outside of the opposite surface of the with it being most preferred that about equal amounts of sulphur and arylhydroxide stabilizer be employed;

The following examples are presented solely for the purpose of further illustrating and disclosing the invention, and are not to be construed as limitations thereon;

Hardness values reported in these examples were made with a standard piece of testing equipment known under the trade designation as Barcol Impressor.

Example I V A solution was prepared from 0.075 part of powdered Cit sulphur, 0.075 part of ditertiary butyl p-cresol, '10 parts of diallyl phthalate monomer, 1 part of lauryl acid peroxide and 1 part of tertiary butyl perbenzoate. The resulting solution was then mixed with a polymerizable composition composed of parts of diallyl pnthalate monomer and 80 parts of dipropylene glycol maleate and the resulting mixture mixed with 400 grams of ground limestone of minus 200 mesh, U.S. Sieve Series; The resulting product was a premix plastic stabilized polyester molding composition. Small balls, about 1 heating at 120 F. for more'than days, had not gelled, as a knife blade could be pushed manually therein and satisfactory moldings were made therefrom. Hardness reading for a cured molding after a 3 minute cure at about 300 F. was 67 on the Barcol scale. In comparison, moldings made from freshly prepared like compositions, except'that they contained no stabilizer or conventional stabilizers, and using 2 to 3 minute cures at about 300 had hardnesses of from 67 to-7 3 on the Barcol scale. These'rnolding tests and hardness values illustrate that the stabilizer combination of the invention exerted little or no detrimental effect on the molding conditions and resulting molded product. ll of the preceding Barcol hardness values were substantially the same, being within the limits of experimental error.

Whena premixed composition was prepared as above, except that the sulphur and the ditertiary butyl p-cresol were. omitted, the unstabilized composition gelled after less than 16 hours at 120 F. to such an extent that a knife blade could not be pressed manually therein and Example 11 Premixstabilizedpolyester molding compositions with the stabilizer combination of Example I were prepared as in Example I, except that the 1 part of tertiary butyl perbenzoate was omitted and there were employed 2 parts .of lauryl acid peroxide. Like compositions also were prepared, except that the stabilizer combination consisted of powdered sulphur and ditertiary butyl pcresol in an amount of 0.15 part of each, These premix compositions were stable for 6.0 and 90 minutes respectively, at 180 F. and 75 and 135 minutes, respectively, at'l70 F. at which times it was possible to pusha toothpick through small about 1 inch diameter balls of these compositions. a Incontrast, likeprem-ix compositions containing 0.075, 0.15 and 0.3.part of powdered sulphur, after 40, 55, and

80 minutes, respectively, at 180 F.-and 45, 70; and 120,.

minutes, respectively at 170 F. had gelled'to such an extent that it was, not possible to push a toothpick through smallabout l inchjdiameter balls thereof; Like premix compositions containing only ditertiary butyl p-cresol in to 1 /2. in diameter, of this premix composition, after Example Ill v A premix stabilized polyester composition was prepared as in Example 1 except that 0.075 part of guaiacol replaced the 0.075 part of tertiary butyl p-cresol. Small portions of this premixed stabilized polyester molding composition inlmasses of more than A" in thickness were stable at 180 F. for over 90 minutes. After the exposure at 180 F. for 90 minutes these masses were found not to contain any hard, preset lumpsor stones; a knife bladecould be pushed manually therethrough; and satisfactory moldings at normal molding conditions were prepared therefrom. The Barcol hardness of moldings having 20 second and 60-sccond cures at about 300 F. were 71 for each. v

In contrast thereto, masses of more than 4" thickness of like compositions except that the stabilizer combination of the invention was replaced by 0.075 part and 0.15 part respectively of guaiacol, after less than about minutes at 180 F, had gelled to such an extent that a knife blade could not be pushed manually therethrough and moldings could not be made therefrom. Masses of more than Mi" in thickness of like compositions except 7 that 0.075 and 0.15 part of sulphur replaced the stabilizer combination of the invention, after less than minutes at 180 F. had gelled to such an extent that a' knife blade could not be pushed manually therethrough and'moldings could not be produced therefrom.

It has been found that stability testing of premix sta-' bilized polyester molding compositions at elevated temperatures substantially below normal molding temperatures provides a reasonably satisfactory basis for estimating the stability of the premix compositions at room temperature. Estimates of room temperature stability follow the assumption that the rate of deterioration of such premix catalyzed composition diminishes as the temperature is lowered, usually about one-half for every 10 F. lowering of temperature. In general, the stability of premix catalyzed polyester compositions is about twice as great at normal room temperature F.) as at F. temperature, about 30 or more times as great at normal room temperature as at F., and about 2000 or more times as great at normal room temperature as at about F. Stability testing of apparently identical samples at 70 F;, 120 F. and 180 F. has confirmed the apparent validity .ofthis'estimation method, as stabilities of various premix catalyzed polyester compositions at room temperatures have averaged about 30 times the stabilities obtained at about 120 F. and about 2000 times the stabilities obtain'ed at about 180 ,F. for the same premix composition.

Example IV Each of the stabilizer combinations employed in Examples 1,11, 111, was incorporated in a premix plastic stabilized polyester molding composition, sold commercially under the name Glaskyd 1901. Glaskyd 1901, a glass fiber reinforced polyester resin molding compound, supplied in forms ranging from /2" diameter rope up to 2 /2" diameter log, contains an organic peroxide catalyst, an unsaturated polyester ,resin and a monomeric vinyl compound polymerizable with the polyester. When compositions containing these stabilizer compositions of the invention'were cured at the moldingconditions recom: mended by the supplier, the physical properties of the cured products'were substantially the same as the properties of products of Glaskycl 1901' not so stabilized. Trade literature of the. supplier has stated the useful life of Glaskyd 1901 to be from one to two months at those temperatures encountered molding shops. In contrast the 

1. A METHOD OF CONSTRUCTING A FURNACE PART OF THE TYPE COMPRISING A REFRACTORY MATERIAL ENCLOSED IN A PAN-LIKE METALLIC SHELL, WHICH COMPRISES (1) INTRODUCING INTO THE SHELL A BODY OF MOIST, PLASTIC HEAT-HARDENABLE REFRACTORY MATERIAL CONTAINING SODIUM SILICATE AS A BONDING AGENT, (A) ONE FACE OF THE BODY OF REFRACTORY BEING EXPOSED AND ALL OTHER FACES THEREOF BEING COVERED BY THE SHELL, (2) AND DRYING AND HARDENING SAID REFRACTORY SUBSTANTIALLY WITHOUT BUCKLING AND FORMATION THEREIN OF LAMINATION BY IRRADIATING ONLY THE EXPOSED FACE THEREOF WITH INFRA-RED ENERGY, SAID IRRADIATION, (A) BEING FROM A SOURCE AT A TEMPERATURE ABOVE 1000*F., AND (B) RAISING THE TEMPERATURE OF AN UPPER QUARTERINCH OF THE REFRACTORY BODY ADJACENT ITS EXPOSED SURFACE AT AN AVERAGE RATE OF AT LEAST ABOUT 115* F. PER HOUR. 